You can rename a root folder or a custom folder, but you cannot rename a folder provided with the stock Catalogs.
To rename a folder
The Library page displays.
The folder name can be a maximum of 255 characters, and all alphanumeric and special characters that you can enter using the keyboard are permitted except for double-quotes ("") and the backslash (\). In addition, the name must be unique with respect to all other folders in the same location in the Catalog. However, case-sensitivity is considered when determining uniqueness; for example, "Sample Curricula" and "Sample curricula" are considered two unique names.
Note: The Library is not updated with your changes until you exit the Library page.